solubility and molarity

[sixpence]

Heating a solution with a salt results in, for the purposes of my question, three things:
increase in solubility of the salt
increase in volume of the solution --> decrease in density, decrease in molarity of the solution

my question is, does molarity count only dissolved solute or does it include precipitated solute as well?

so in other words, if solubility of a salt decreases, without a change in volume, does molarity also decrease? i think this is an easy question but i can't think right now

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[loveoforganic]

Molarity increases until you reach saturation.

 

[chemtopper]

Molarity means how many moles of the solute are there in the given volume of the solution.
From here you can say as the solubility decreases ,molarity will also decrease
and as solubility increases ---more moles of solute in solution so molarity increases.
I hope it is clear now.

 

[sixpence]

so what happens when you increase the temp. because the solubility will increase, increasing molarity, but at the same time the volume increases, decreasing molarity and decreasing density. those two are going against each other right? do you have to calculate each problem to see which has a greater effect or is there a general rule?

 

[loveoforganic]

Liquids don't tend to expand much upon heating. Solubility has the potential to increase pretty drastically.

 

[wanderer]

so what happens when you increase the temp. because the solubility will increase, increasing molarity, but at the same time the volume increases, decreasing molarity and decreasing density. those two are going against each other right? do you have to calculate each problem to see which has a greater effect or is there a general rule?

Think of dissolution in terms of dG. dG = dH - TdS. Dissolution of a solid almost always leads to an increase in entropy. As temperature increases, the entropy aspect becomes more significant.